Cache management on high availability routers in a content centric network

ABSTRACT

One embodiment provides a forwarding device, comprising a plurality of components, including one or more line cards and a supervisor card. An ingress line card receives a content object with a name. In response to determining a distributed storage technique, a selected line card stores the content object in a location which is a cache of the selected line card. The selected line card creates a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored. The selected line card transmits a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry. A respective other component creates a second entry in a table for the respective other component, wherein the second entry matches the first entry.

RELATED APPLICATIONS

The subject matter of this application is related to the subject matter in the following applications:

-   -   U.S. patent application Ser. No. 13/847,814 (Attorney Docket No.         PARC-20120537-US-NP), entitled “ORDERED-ELEMENT NAMING FOR         NAME-BASED PACKET FORWARDING,” by inventor Ignacio Solis, filed         20 Mar. 2013 (hereinafter “U.S. patent application Ser. No.         13/847,814”); and     -   U.S. patent application Ser. No. 12/338,175 (Attorney Docket No.         PARC-20080626-US-NP), entitled “CONTROLLING THE SPREAD OF         INTERESTS AND CONTENT IN A CONTENT CENTRIC NETWORK,” by         inventors Van L. Jacobson and Diana K. Smetters, filed 18 Dec.         2008 (hereinafter “U.S. patent application Ser. No.         12/338,175”);         the disclosures of which are herein incorporated by reference in         their entirety.

BACKGROUND Field

This disclosure is generally related to distribution of digital content. More specifically, this disclosure is related to cache management on high availability routers in a content centric network.

Related Art

The proliferation of the Internet and e-commerce continues to create a vast amount of digital content. Content centric network (CCN) architectures have been designed to facilitate accessing and processing such digital content. A CCN includes entities, or nodes, such as network clients, forwarders (e.g., routers), and content producers, which communicate with each other by sending interest packets for various content items and receiving content object packets in return. CCN interests and content objects are identified by their unique names, which are typically hierarchically structured variable length identifiers (HSVLI). An HSVLI can include contiguous name components ordered from a most general level to a most specific level.

A CCN entity (such as a router) typically maintains three data structures: a pending interest table (PIT) to track incoming and pending requests for data; a forwarding information base (FIB) which determines interfaces on which to forward a packet; and a cache or a content store (CS) for storing data which may be retrieved in response to an interest. Typical CCN communication is described in U.S. patent application Ser. No. 13/847,814. While current CCN protocols specify that a router may store received content in its CS, the current CCN protocols do not specify where or how to store the content in a high availability router, i.e., in a router with multiple intelligent network line cards which are connected to a supervisor card via dedicated lanes through a fabric. Nor do current CCN protocols specify how to subsequently access such stored content in a high availability router.

SUMMARY

One embodiment provides a forwarding device, comprising a plurality of components, including one or more line cards and a supervisor card, wherein the components perform a method. An ingress card of the forwarding device receives a content object with a name. In response to determining a distributed storage technique, a selected line card stores the content object in a location which is a cache of the selected line card. The selected line card creates a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored. The selected line card transmits a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry. A respective other component creates a second entry in a table for the respective other component, wherein the second entry matches the first entry.

In some embodiments, the selected line card is one or more of the ingress line card and an egress line card. If the selected line card is the egress line card, the ingress line card transmits the content object to the egress line card. If the selected line card is both the ingress line card and the egress line card: storing the content object, creating the first entry, and transmitting the first notification message are performed by the ingress line card; and storing the content object, creating the first entry, and transmitting the first notification message are performed by the egress line card.

In some embodiments, the selected line card marks the first entry as active, and multicasts the first notification message to the other components.

In some embodiments, the selected line card marks the first entry as inactive. The selected line card transmits to the supervisor card a request to cache the content object at the location. In response to accepting, by the supervisor card, the request to cache the content object at the location: the supervisor card multicasts the first notification message to the other components; the selected line card marks the first entry as active; and the respective other component creates the second entry in the table for the respective other component.

In some embodiments, in response to not accepting, by the supervisor card, the request to cache the content object at the location, the selected line card removes the first entry from the table of the selected line card based on a timeout of the first entry.

In some embodiments, in response to determining a centralized storage technique, the ingress line card transmits the content object to the supervisor card. The supervisor card stores the content object in a central location which is associated with the supervisor card. The supervisor card creates a third entry in a table of the supervisor card, wherein the third entry indicates the content object name and further indicates the supervisor card as the central location in which the content object is stored. The supervisor card transmits a second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry. A respective other component creates a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry.

In some embodiments, the central location is one or more of: a cache on the supervisor card; an external storage device attached to the supervisor card; an external storage device attached to a line card; and a dedicated line card for storage, wherein the dedicated line card is accessed only by the supervisor card.

In some embodiments, if the central location is the external storage device attached to the supervisor card, the external storage device attached to the line card, or the dedicated line card for storage, the supervisor card transmits the content object to the central location.

In some embodiments, the external storage device attached to the line card or the dedicated line card for storage creates the third entry in a table of the external storage device attached to the line card or the dedicated line card for storage. The external storage device attached to the line card or the dedicated line card for storage transmits the second notification message to the other components.

In some embodiments, transmitting the second notification message further comprises multicasting, by the supervisor card, the second notification message to the other components.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an exemplary network which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention.

FIG. 1B illustrates an exemplary network which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention.

FIG. 2A illustrates an exemplary high availability router which facilitates cache management, in accordance with an embodiment of the present invention.

FIG. 2B illustrates an exemplary high availability router which facilitates cache management, including distributed cache management, in accordance with an embodiment of the present invention.

FIG. 2C illustrates an exemplary high availability router which facilitates cache management, including centralized cache management, in accordance with an embodiment of the present invention.

FIG. 2D illustrates an exemplary high availability router which facilitates cache management, including an exemplary named data cache location table, in accordance with an embodiment of the present invention.

FIG. 3A illustrates an exemplary named data cache location table, in accordance with an embodiment of the present invention.

FIG. 3B illustrates an exemplary named data cache location table, including multiple entries for the same named data, in accordance with an embodiment of the present invention.

FIG. 4A presents a flow chart illustrating a method for processing a content object, including distributed cache management, in accordance with an embodiment of the present invention.

FIG. 4B presents a flow chart illustrating a method for processing a content object, including distributed cache management and distribution methods, in accordance with an embodiment of the present invention.

FIG. 5A presents a flow chart illustrating a method for processing a content object, including centralized cache management, in accordance with an embodiment of the present invention.

FIG. 5B presents a flow chart illustrating a method for processing a content object, including centralized cache management, in accordance with an embodiment of the present invention.

FIG. 5C presents a flow chart illustrating a method for processing a content object, including centralized cache management where the central location is an external storage device attached to a line card or a dedicated line card, in accordance with an embodiment of the present invention.

FIG. 6 presents a flow chart illustrating a method for processing an interest, in accordance with an embodiment of the present invention.

FIG. 7A presents a flow chart illustrating a method for handling removal of an entry from a named data cache location table, in accordance with an embodiment of the present invention.

FIG. 7B presents a flow chart illustrating a method for handling initialization of a new line card, in accordance with an embodiment of the present invention.

FIG. 7C presents a flow chart illustrating a method for handling the loss of an existing line card, in accordance with an embodiment of the present invention.

FIG. 8 illustrates an exemplary computer system which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention.

In the figures, like reference numerals refer to the same figure elements.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the embodiments, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Overview

Embodiments of the present invention provide a system which facilitates efficient cache management of high availability routers in a content centric network (CCN). A CCN entity (such as a router) typically maintains three data structures: a pending interest table (PIT) to track incoming and pending requests for data; a forwarding information base (FIB) which determines interfaces on which to forward a packet; and a cache or a content store (CS) for storing data which may be retrieved in response to an interest. CCN communication is described in U.S. patent application Ser. No. 13/847,814.

A typical high availability router (such as a carrier-class router) may offer terabits of switching capacity, and can include multiple components, including intelligent network line cards which are connected to a supervisor card or a control card via dedicated lanes through the fabric. A line card which receives content in from another device is referred to as an ingress line card, and a line card which transmits content out to another device is referred to as an egress line card. Content can include a CCN packet (e.g., interests and content objects), where a packet has a name (“named data”). A line card can serve as both an ingress and an egress line card for a CCN packet.

Current CCN protocols do not specify where and how to store content in the router, or specifically, in the CS of the router. Nor do current CCN protocols specify how to subsequently access such stored content in a high availability router. Embodiments of the present invention provide a system which allows a high availability router in a CCN to store named data based on either a distributed or a centralized manner, and associated with components (e.g., line cards or a supervisor card) of the router. The system also provides inter-component notification of where incoming content is stored, and component-specific tables which map named data to its stored location. This allows the system to subsequently receive and process an incoming interest. That is, an ingress line card which receives an interest with a name (i.e., named data) can access the requested content by performing a lookup in the component-specific table for the named data to obtain the corresponding cache location, and subsequently send the interest to the listed component to retrieve the requested content.

In distributed cache management, content may be stored on an ingress line card, an egress line card, or both an ingress and an egress line card. Distributed cache management is described below in relation to FIGS. 4A-4B. In centralized cache management, content may be stored in one of four locations, which are each associated with the supervisor card: (a) a cache on the supervisor card; (b) an external storage device attached to the supervisor card; (c) an external storage device attached to a line card; and (d) a dedicated line card for storage, where the dedicated line card can only be accessed by the supervisor card. Distributed cache management is described below in relation to FIGS. 5A-5C.

Thus, the present system provides improvements to the distribution of digital content, where the improvements are fundamentally technological. Embodiments of the present invention provide a technological solution (e.g., caching content in various locations associated with a high availability router based on a distributed or a centralized manner, providing inter-component notification of where content is cached, and maintaining component-specific tables which map named data to its cache location) to the technological problem of the efficient, secure, and effective distribution and storage of digital content.

In CCN, each piece of content is individually named, and each piece of data is bound to a unique name that distinguishes the data from any other piece of data, such as other versions of the same data or data from other sources. This unique name allows a network device to request the data by disseminating a request or an interest that indicates the unique name, and can obtain the data independent from the data's storage location, network location, application, and means of transportation. The following terms are used to describe the CCN architecture:

Content Object (or “content object”): A single piece of named data, which is bound to a unique name. Content Objects are “persistent,” which means that a Content Object can move around within a computing device, or across different computing devices, but does not change. If any component of the Content Object changes, the entity that made the change creates a new Content Object that includes the updated content, and binds the new Content Object to a new unique name.

Unique Names: A name in a CCN is typically location independent and uniquely identifies a Content Object. A data-forwarding device can use the name or name prefix to forward a packet toward a network node that generates or stores the Content Object, regardless of a network address or physical location for the Content Object. In some embodiments, the name may be a hierarchically structured variable-length identifier (HSVLI). The HSVLI can be divided into several hierarchical components, which can be structured in various ways. For example, the individual name components parc, home, ccn, and test.txt can be structured in a left-oriented prefix-major fashion to form the name “/parc/home/ccn/test.txt.” Thus, the name “/parc/home/ccn” can be a “parent” or “prefix” of “/parc/home/ccn/test.txt.” Additional components can be used to distinguish between different versions of the content item, such as a collaborative document. The HSVLI can also include contiguous name components ordered from a most general level to a most specific level, and a name prefix can be one or more of the contiguous name components beginning from the most general level.

In some embodiments, the name can include an identifier, such as a hash value that is derived from the Content Object's data (e.g., a checksum value) and/or from elements of the Content Object's name. A description of a hash-based name is described in U.S. patent application Ser. No. 13/847,814, which is herein incorporated by reference. A name can also be a flat label. Hereinafter, “name” is used to refer to any name for a piece of data in a name-data network, such as a hierarchical name or name prefix, a flat name, a fixed-length name, an arbitrary-length name, or a label (e.g., a Multiprotocol Label Switching (MPLS) label).

Interest (or “interest”): A packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or Interest across an information-centric network, which CCN/NDN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or Interest.

Face or Interface (or “face” or “interface”): In CCN, the term “face” is a generalization of the concept of an interface. A face may be a connection to a network or directly to an application party. A face may be configured to send and receive broadcast or multicast packets on a particular network interface, or to send and receive packets using point-to-point addressing in the underlying transport, or using a tunnel (for example a TCP tunnel). A face may also be the connection to a single application process running on the same machine, via an encapsulation like UDP or an OS-specific inter-process communication path. All messages arrive through a face and are sent out through a face. In this disclosure, the term “neighbor” is interchangeable with the terms “face” and “interface,” referring to an incoming or outgoing interface of an Interest.

“Prefix”: In this disclosure, the term “prefix” can be used to refer to either a name of a specific content object or a name prefix for the content object. A routable name prefix can determine the routing of a packet that indicates a request for a piece of data, and includes a name (or a name prefix) for the piece of data. A data consumer can disseminate a request or interest across an information-centric network, which CCN/NDN routers can propagate toward a storage device (e.g., a cache server) or a data producer that can provide the requested data to satisfy the request or interest.

The methods disclosed herein are not limited to CCN networks and are applicable to other architectures as well. A description of a CCN architecture is described in U.S. patent application Ser. No. 12/338,175, which is herein incorporated by reference.

Exemplary Network and Communication

FIG. 1A illustrates an exemplary network 100 which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention. Network 100 can include a consumer or content requesting device 116, a producer or content producing device 118, and a router or other forwarding device at nodes 102, 104, 106, 108, 110, 112, and 114. A forwarding device can be a router, a switch, or any computing device which can forward packets. A node can be a computer system, an end-point representing users, and/or a device that can generate interests or originate content. A node can also be an edge router (e.g., CCN nodes 102, 104, 112, and 114) or a core router (e.g., intermediate CCN routers 106, 108, and 110). Network 100 can be a content centric network. Recall that a CCN entity can maintain a pending interest table (PIT), a forwarding information base (FIB), and a content store (CS).

During operation, content requesting device 116 can generate an interest 150 with a name 152 of “/parc/documents” and an optional payload 154 of “<data>.” Interest 150 can travel through network 100, via routers or nodes 102, 110, and 112, before reaching content producing device 118. A node which receives an interest can process the interest based on standard CCN rules. For example, upon receiving interest 150, node 110 can perform a CS lookup to see if the requested content is cached. If so, node 110 can return the cached content on a reverse path as interest 150. If not, node 110 can perform a PIT lookup to see if there is a matching interest for the requested content. If a matching PIT entry exists, node 110 can aggregate the arrival interface of interest 150 with the already existing arrival interfaces listed in the matching PIT entry. If a matching PIT entry does not exist, node 110 can perform a FIB lookup to obtain the next hop to which to forward interest 150. If there is a FIB entry, node 110 can create a new PIT entry and forward interest 150; if there is no FIB entry, node 110 can drop interest 150. Furthermore, upon aggregating the arrival interface and finding a matching FIB entry, node 110 can forward interest 150 via the next hop indicated in the matching FIB entry (e.g., via the interface corresponding to node 112).

Interest 150 can reach producer 118, which can perform the same processing as described above for node 110. Producer 118 can perform a lookup in its CS, determine a cache hit, and return a responsive content object 160 with a name 162 of “/parc/documents” and a payload 164 of “<data>.” Producer 118 can transmit content object 160 through network 100 on a reverse path as interest 150, i.e., via nodes 112, 110, and 102, before reaching device 116. A node which receives a content object can process the content object based on standard CCN rules. For example, upon receiving content object 160, node 110 can perform a PIT lookup to see if there is a matching interest for the received content. If not, node 110 can drop content object 160. If there is a matching PIT entry, node 110 “consumes” the PIT entry by transmitting content object 160 via the arrival interfaces listed in the matching PIT entry.

Node 110 can also store content object 160 in its CS. Current CCN protocols do not specify how or where content object 160 may be stored. Embodiments of the present invention allow a router (such as node 110) to store named content (such as content object 160) in various ways, including a distributed manner and a centralized manner, as described below in relation to FIGS. 4A-4B and FIGS. 5A-5C, respectively.

FIG. 1B illustrates an exemplary network 100 which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention. Subsequent to the communication of FIG. 2A, a node may receive an interest for content, where the requested content already exists in a CS of the node. For example, a consumer or content requesting device 120 can generate an interest 170 with a name 172 of “/parc/documents” and an optional payload 174 of “<data>.” Interest 170 can travel through network 100, via intermediate routers or nodes 104, 108, and reach node 110. Node 110 can perform a lookup in its CS, determine a cache hit, and return a responsive content object 160 with a name 162 of “/parc/documents” and a payload 164 of “<data>.” Recall that node 110 has previously stored content object 160 in its CS, as described in relation to FIG. 1A. Current CCN protocols do not specify how a stored content object is subsequently accessed. Embodiments of the present invention allow content to be stored by high availability routers (such as node 110) in various locations, as associated with components of the router (e.g., line cards or a supervisor card). The system also provides component-wide notification of where named data is stored so that the named data content may be subsequently retrieved. Upon retrieving content 160 from its CS, node 110 can transmit content object 160 through network 100 on a reverse path as interest 170, i.e., via nodes 108 and 104, before reaching device 120.

Exemplary High Availability Routers and Cache Locations

FIG. 2A illustrates an exemplary high availability router 200 which facilitates cache management, in accordance with an embodiment of the present invention. Router 200 can include multiple line cards (such as a line card 210 and a line card 220) and a supervisor card 230. Line card 210 can include: a network processing unit (NPU) 212 which includes outward facing media ports for receiving and transmitting data packets; a central processing unit (CPU) 214; a CCN engine 216 for performing CCN-related tasks, such as verifying and processing an interest or content object; and a Q-Engine FIC 218 which interfaces with supervisor card 230 via a fabric 232 of supervisor card 230. Supervisor card 230 can also include a CPU 234. Note that CCN engine 216 and CPU 214 are depicted as separate entities in line card 210. However, CCN processing may be folded into CPU 214. Router 200 depicts a sample configuration for a typical multi-card chassis router. Other configurations are possible. Furthermore, while router 200 depicts a single supervisor card 230, a high availability router typically includes multiple supervisor cards, one of which may serve as the active supervisor card (such as supervisor card 230) and the others which may be serve as standby cards (not depicted).

Line card 210 depicts the ingress of interest 150 and the egress of content object 160, while line card 220 depicts the egress of interest 150 and the ingress of content object 160. Note that a line card can serve as both an ingress and an egress line card for both interests and content objects. FIG. 2A depicts line card 210 as the interest ingress and the content egress, and depicts line card 220 as the interest egress and the content ingress, as an example only.

FIG. 2B illustrates an exemplary high availability router 200 which facilitates cache management, including distributed cache management, in accordance with an embodiment of the present invention. In distributed cache management, the cache can reside on an ingress line card, an egress line card, or both the ingress line card and the egress line card. Router 200 can include a cache 251 on line card 220, which corresponds to an ingress line card cache for content object 160. Router 200 can include a cache 252 on line card 210, which corresponds to an egress line card cache for content object 160. Router 200 can also include both cache 251 and cache 252. Distributed cache management is described below in relation to FIGS. 4A and 4B.

FIG. 2C illustrates an exemplary high availability router 200 which facilitates cache management, including centralized cache management, in accordance with an embodiment of the present invention. In centralized cache management, the cache can reside on the supervisor card, an external storage device attached to the supervisor card, an external storage device attached to a line card, or a dedicated line card which has no front face. Router 200 can include a cache 254 on supervisor card 230. Router 200 can include a cache 255 which is an external storage device attached to supervisor card 230. Router 200 can include a cache 256 which is an external storage device attached to line card 220. Router 200 can include a cache 257 on a dedicated line card 240 with no front face and only a connection to supervisor card 230 via fabric 232.

FIG. 2D illustrates an exemplary high availability router which facilitates cache management, including an exemplary named data cache location table, in accordance with an embodiment of the present invention. Line card 210 can include a named data cache location table 280. Table 280 can reside in cache 252 as depicted, or can reside elsewhere on line card 210. Table 280 can include entries with a name of data 282 and a cache location 284. Location 284 can indicate one of several values: “Local” indicates that the named data is stored on that local line card; “Supervisor” indicates that the named data is stored on the supervisor card; and “Line Card x” indicates that the named data is stored on Line Card x. Each router component can maintain its own copy of the named data cache location table, regardless of whether a respective component stores any content (i.e., any named data included in the named data cache location table) in its cache. Furthermore, in this disclosure, a first entry “matches” a second entry when the location indicates the same location. For example, named data cache location table 280 of line card 210 includes a first entry 291 for named data “/parc/printer” with a location of “Local,” which indicates Line Card 210. A second entry in a named data cache location table of line card 220 is said to “match” entry 291 if the second entry includes a cache location of “Line Card 210” (not shown).

Exemplary Named Data Cache Location Tables

FIG. 3A illustrates an exemplary named data cache location table 300, in accordance with an embodiment of the present invention. Table 300 can include entries with a name of data (or “data name”) 302 and a cache location 304. For example: entry 311 can include a data name “/parc/printer” and a cache location of “Local”; entry 312 can include a data name “/parc/calendar” and a cache location of “Supervisor”; and entry 313 can include a data name “/parc/documents” and a cache location of “Line Card 14.”

In some embodiments, multiple interests for the same content may be re-routed due to routing changes, which may result in multiple copies of the content being received and stored in multiple locations. Thus, table 300 can include entries with multiple locations. For example, entry 314 can include a data name of “/parc/services” and a cache location of “{Local, Line Card 8}.”

FIG. 3B illustrates an exemplary named data cache location table 320, including multiple entries for the same named data, in accordance with an embodiment of the present invention. Table 320 can include entries with a data 322 and a cache location 324. Table 320 can indicate multiple entries for the same named data. For example, table 320 can include entry 321 with a data name “/parc/services” and a cache location of “Local,” and table 320 can also include an entry 322 with a data name “/parc/services” and a cache location of “Line Card 8.”

High Availability Router Facilitates Distributed Cache Management

FIG. 4A presents a flow chart 400 illustrating a method for processing a content object, including distributed cache management, in accordance with an embodiment of the present invention. During operation, the system receives, by an ingress line card of a forwarding device, a content object with a name, wherein the forwarding device comprises a plurality of components, including one or more line cards and a supervisor card (operation 402). The system verifies, by the ingress line card, the content object by computing a content object hash (COH) value of the received content object and comparing the computed COH value against an expected (and previously determined) COH for the content object (operation 404). The system optionally determines a distributed storage technique for the content object (operation 406). The system stores, by a selected line card, the content object in a location which is a cache of the selected line card (operation 408). The selected line card can be the ingress line card, an egress line card, or both the ingress and the egress line card. The system creates, by the selected line card, a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored (operation 410). The system transmits, by the selected line card, a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry (operation 412). Subsequently, the system creates, by a respective other component, a second entry in a table for the respective other component, wherein the second entry matches the first entry (operation 414). This facilitates CCN cache management on a high availability router.

FIG. 4B presents a flow chart 420 illustrating a method for processing a content object, including distributed cache management via an ingress line card and distribution methods, in accordance with an embodiment of the present invention. Flow chart 420 assumes that the system (via the ingress line card) has already received and verified the content object (operations 402 and 404 of FIG. 4A), and optionally determines a distributed storage technique for the content object (operation 406 of FIG. 4A). During operation, the system stores, by a selected line card which is the ingress line card, the content object in a cache of the ingress line card (operation 422). The system creates, by the ingress line card, a first entry in a table of the ingress line card, wherein the first entry indicates the content object name and the ingress line card as the location in which the content is stored (e.g., “Local”) (operation 424). The system notifies, by the ingress line card, the other components of the creation of the first entry, via a multicast or a unicast method (operation 426).

The system can multicast the notification of the creation of the first entry. The system marks, by the ingress line card, the first entry as active (operation 428). The system multicasts, by the ingress line card, the first notification message to the other components (including the supervisor card) (operation 430). The supervisor card is not only one of the “other” components which receives the notification message, but is also notified in a specific way regardless of whether the system caches content in a distributed or a centralized manner, and also regardless of whether the notification message is distributed via multicast or unicast. Thus, the supervisor card always possesses the most current and up-to-date version of the table, which allows the supervisor card to provide redundancy in the system.

The system receives, by each respective other component, the first notification message (operation 432). A respective other component can receive the notification message and send it to its local CCN Engine (e.g., CCN engine 216 of line card 210 of FIG. 2B). The system saves, by each respective other component, the first entry in a table of the respective other component (operation 434).

The system can also unicast the notification of the creation of the first entry. The system marks, by the ingress line card, the first entry as inactive (operation 442). The system transmits, by the ingress line card to the supervisor card, a request to cache the content object at the ingress line card (operation 444). If the supervisor card does not accept the request (decision 446), the operation returns. The system does nothing (i.e., takes no action), and the inactive first entry eventually times out and is removed by the ingress card. If the supervisor card accepts the request (decision 446), the system multicasts, by the supervisor card, the first notification message to the other components (operation 448). The system receives, by the ingress line card, the first notification message, and updates the first entry as active (operation 450). The operation then continues as described at operation 432, where each respective other component receives the first notification message (operation 432) and saves the first entry in a table of the respective other component (operation 434).

FIG. 4B depicts the operations that occur when the system determines to store the received and verified content in a cache of the ingress line card. The system can also determine to store the received and verified content in a cache of the egress line card. The egress line card performs operations similar to the operations performed by the ingress line card, as described above for operations 422-426 (i.e., storing the content or named data, creating a table entry, and notifying the other components), operations 428-434 (i.e., notification via multicast), and operations 442-450 (i.e., notification via unicast). In addition, the system can determine to store the received and verified content in both a cache of the ingress line card, and a cache of the egress line card, whereby the system performs the operations corresponding to each of the ingress line card and the egress line card.

High Availability Router Facilitates Centralized Cache Management

FIG. 5A presents a flow chart 500 illustrating a method for processing a content object, including centralized cache management, in accordance with an embodiment of the present invention. During operation, the system receives, by an ingress line card of a forwarding device, a content object with a name, wherein the forwarding device comprises a plurality of components, including one or more line cards and a supervisor card (operation 502). The system verifies, by the ingress line card, the content object by computing a COH value of the received content object and comparing the computed COH value against an expected (and previously determined) COH for the content object (operation 504). If the system does not find a matching entry based on the name in the PIT (decision 506), the system discards the content object (operation 508), and the operation returns. In some embodiments, even if no matching PIT entry exists, the system may still send the content object to the supervisor card for processing or caching, depending on a policy of the router. If the system does find a matching PIT entry (decision 506), the system optionally determines a centralized storage technique for the content object (operation 510). The system can store the content object in either a distributed manner (as depicted in FIGS. 4A-4B) or in a centralized manner (as depicted in FIGS. 5A-5C).

The system transmits, by the ingress line card, the content object to one or more interfaces listed in the matching PIT entry (operation 512). The system also transmits, by the ingress line card, the content object to the supervisor card (operation 514), and the operation continues as depicted at Label A of FIG. 5B. Note that the one or more interfaces can correspond to one or more egress line cards, and the ingress line card can transmit the content object to both the supervisor card and the egress line cards via unicast or multicast to groups of two or more cards.

FIG. 5B presents a flow chart 520 illustrating a method for processing a content object, including centralized cache management, in accordance with an embodiment of the present invention. During operation, the system stores, by the supervisor card, the content object in a central location which is associated with the supervisor card (operation 522). The central location which is associated with the supervisor card can be one or more of: (a) a cache on the supervisor card; (b) an external storage device attached to the supervisor card; (c) an external storage device attached to a line card; and (d) a dedicated line card for storage. In some embodiments (e.g., for central locations (b), (c), and (d) above), the supervisor card transmits the content object to the central location. The system creates, by the supervisor card, a third entry in a table of the supervisor card, wherein the third entry indicates the content object name and further indicates the supervisor card as the location in which the content object is stored (operation 524). The system transmits, by the supervisor card, a second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry (operation 526). Subsequently, the system creates, by a respective other component, a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry (operation 528). Transmitting the second notification message to central locations (c) and (d) is described below in relation to FIG. 5C.

FIG. 5C presents a flow chart 540 illustrating a method for processing a content object, including centralized cache management where the central location is an external storage device attached to a line card or a dedicated line card, in accordance with an embodiment of the present invention. During operation, the system receives, by an ingress line card of a forwarding device, a content object with a name, wherein the forwarding device comprises a plurality of components, including one or more line cards and a supervisor card (operation 502). The system verifies, by the ingress line card, the content object by computing a COH value of the received content object and comparing the computed COH value against an expected (and previously determined) COH for the content object (operation 504). The system transmits, by the ingress line card, the content object to the supervisor card (operation 514). The system stores, by the supervisor card, the content object in a central location which is associated with the supervisor card, wherein the central location is an external storage device attached to a line card or a dedicated line card for storage (operation 542).

The system transmits, by the supervisor card, the content object to the central location (i.e., the external storage attached to the line card or the dedicated line card) (operation 544). The system creates, by the external storage device attached to the line card or by the dedicated line card, the third entry in a table of the external storage attached to the line card or the dedicated line card (operation 546). In some embodiments, the third entry can indicate the content object name and can further indicate the external storage device attached to the line card or the dedicated line card as the central location associated with the supervisor card in which the content object is stored. The system transmits, by the external storage device attached to the line card or by the dedicated line card, the second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry (operation 548). Subsequently, the system creates, by a respective other component, a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry (operation 550).

High Availability Router Processes Interest

FIG. 6 presents a flow chart 600 illustrating a method for processing an interest, in accordance with an embodiment of the present invention. During operation, the system receives, by an ingress line card of a forwarding device, an interest with a name, wherein the forwarding device comprises a plurality of components, including one or more line cards and a supervisor card (operation 602). The system processes, by the ingress line card, the interest based on standard CCN rules (operation 604). The system performs a lookup in the named data cache location table (or cache location table) for a matching entry (operation 606) (i.e., to determine whether a matching entry exists). If a matching entry does not exist (decision 608) (implying a cache miss), the system processes the interest based on standard CCN rules (operation 610), as described above in relation to FIGS. 1A and 1B. If a matching entry does exist in the cache location table (decision 608), the system can operate based on where the content is stored. If the matching entry indicates that the named data is stored locally (i.e., on the local ingress line card), the system retrieves, by the ingress line card, the content object via a lookup in the local cache (operation 612). The system transmits, by the ingress line card, the content object via the incoming media port or arrival interface of the interest (operation 614).

If the matching entry indicates that the named data is stored on a remote line card (i.e., on an egress line card), the system transmits, by the requesting line card (i.e., the ingress line card), the interest to the remote line card (operation 622). The system retrieves, by the remote line card, the content object via a lookup in the cache of the remote line card (operation 624). The system transmits, by the remote line card, the content object to the requesting line card (i.e., the ingress line card) (operation 626). The system transmits, by the ingress line card, the content object via the incoming media port or arrival interface of the interest (operation 614).

If the matching entry indicates that the named data is stored in a central location which is associated with the supervisor card, the system transmits, by the requesting line card (i.e., the ingress line card), the interest to the supervisor card (operation 632). The system retrieves, by the supervisor card, the content object via a lookup in the central location (operation 634). The system transmits, by the supervisor card, the content object to the requesting line card (i.e., the ingress line card) (operation 636). Finally, the system transmits, by the ingress line card, the content object via the incoming media port or arrival interface of the interest (operation 614).

Exemplary Use Cases

FIG. 7A presents a flow chart 700 illustrating a method for handling removal of an entry from a named data cache location table, in accordance with an embodiment of the present invention. During operation, the system determines, by a component of the forwarding device, an expiration of an entry in a named data cache location table of the component (or cache location table) (operation 702). The component can be a line card or the supervisor card. The system deletes, by the component, the expired entry from the cache location table (operation 704). The system transmits, by the component, a delete notification message for the expired entry to the other components (operation 706). Subsequently, the system deletes, by a respective other component, an entry corresponding to the expired entry from a cache location table of the respective other component (operation 708).

FIG. 7B presents a flow chart 720 illustrating a method for handling initialization of a new line card, in accordance with an embodiment of the present invention. During operation, the system detects, by the supervisor card of the forwarding device, an initialization of a new line card (operation 722). The system transmits, by the supervisor card to the new line card, a copy of the named data cache location table of the supervisor card (operation 724). This allows the new line card to process a subsequent interest for content cached by a component of the forwarding device.

FIG. 7C presents a flow chart 740 illustrating a method for handling the loss of an existing line card, in accordance with an embodiment of the present invention. During operation, the system detects, by the supervisor card of the forwarding device, a loss of an existing line card which stores data listed in the named data cache location table of the supervisor card (operation 742). The system transmits, by the supervisor card, a bulk delete notification message for the lost line card to the other components of the router (operation 744). Subsequently, the system deletes, by a respective other component, all entries corresponding to the lost line card from a cache location table of the respective other component (operation 746).

Note that when a non-hosting line card goes down (i.e., a line card that includes a named data cache location table but that does not store or host any data), the system need not take any actions. In this case, there is no need to send an update to any other line cards.

Exemplary Computer System

FIG. 8 illustrates an exemplary computer system which facilitates cache management on high availability routers in a content centric network, in accordance with an embodiment of the present invention. Computer system 802 includes a processor 804, a memory 806, and a storage device 808. Memory 806 can include a volatile memory (e.g., RAM) that serves as a managed memory, and can be used to store one or more memory pools. Furthermore, computer system 802 can be coupled to a display device 810, a keyboard 812, and a pointing device 814. Storage device 808 can store an operating system 816, a content-processing system 818, and data 832.

Content-processing system 818 can include instructions, which when executed by computer system 802, can cause computer system 802 to perform methods and/or processes described in this disclosure. Specifically, content-processing system 818 may include instructions for sending and/or receiving data packets to/from other network nodes across a computer network, such as a content centric network (communication module 820). A data packet can include an interest packet or a content object packet with a name which is an HSVLI that includes contiguous name components ordered from a most general level to a most specific level.

Furthermore, content-processing system 818 can include instructions for receiving, by an ingress line card of a forwarding device, a content object with a name (communication module 520). Content-processing system 818 can include instructions for in response to determining a distributed storage technique (content-storing module 822): storing, by a selected line card, the content object in a location which is a cache of the selected line card (content-storing module 822); creating, by the selected line card, a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored (location table-managing module 824); transmitting, by the selected line card, a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry (fabric communication module 826); and creating, by a respective other component, a second entry in a table for the respective other component, wherein the second entry matches the first entry (location table-managing module 824).

Content-processing system 818 can also include instructions for transmitting, by the ingress line card, the content object to the egress line card (fabric communication module 826). Content-processing system 818 can include instructions for storing the content object (content-storing module 822), creating the first entry (location table-managing module 824), and transmitting the first notification message (fabric communication module 826) by the ingress line card, and can include further instruction for storing the content object (content-storing module 822), creating the first entry (location table-managing module 824), and transmitting the first notification message (fabric communication module 826) by the egress line card. Content-processing system 818 can also include instructions for marking, by the selected line card, the first entry as active (location table-managing module 824), and for multicasting, by the selected line card, the first notification message to the other components (fabric communication module 826).

Content-processing system 818 can additionally include instructions for marking, by the selected line card, the first entry as inactive (location table-managing module 824). Content-processing system 818 can include instructions for transmitting, by the selected line card to the supervisor card, a request to cache the content object at the location (fabric communication module 826). Content-processing system 818 can include instructions for, in response to accepting, by the supervisor card, the request to cache the content object at the location (fabric communication module 826): multicasting, by the supervisor card, the first notification message to the other components (fabric communication module 826); marking, by the selected line card, the first entry as active (location table-managing module 824); and creating, by the respective other component, the second entry in the table for the respective other component (location table-managing module 824).

Content-processing system 818 can also include instructions for, in response to not accepting, by the supervisor card, the request to cache the content object at the location (fabric communication module 826), removing, by the selected line card, the first entry from the table of the selected line card based on a timeout of the first entry (location table-managing module 824).

Moreover, content-processing system 818 can include instructions for, in response to determining a centralized storage technique (content-storing module 822), transmitting, by the ingress line card, the content object to the supervisor card (fabric communication module 826). Content-processing system 818 can include instructions for storing, by the supervisor card, the content object in a central location which is associated with the supervisor card (content-storing module 822). Content-processing system 818 can include instructions for creating, by the supervisor card, a third entry in a table of the supervisor card, wherein the third entry indicates the content object name and further indicates the supervisor card as the central location in which the content object is stored (location table-managing module 824). Content-processing system 818 can include instructions for transmitting, by the supervisor card, a second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry (fabric communication module 826). Content-processing system 818 can include instructions for creating, by a respective other component, a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry (location table-managing module 824).

Data 830 can include any data that is required as input or that is generated as output by the methods and/or processes described in this disclosure. Specifically, data 830 can store at least: an interest or interest packet; a content object or content object packet; a name; a name that is an HSVLI that includes contiguous name components ordered from a most general level to a most specific level; a name of data, including an interest name or a content object name; an indicator of one or more components of a forwarding device; an indicator of at least one line card; an indicator of an ingress line card, a local line card, a remote line card, or an egress line card; an indicator of a supervisor card, an active supervisor card, or a standby supervisor card; a cache or content store associated with a component; a table mapping a name of data to a location in which the corresponding named data is stored; an entry in the table; a field or indicator of an entry with an active or inactive status; a notification message; a notification message which indicates a name of data and a location in which the named data is stored; a request to cache a content object at a location; a response to the request to cache a content object at a location; a central location associated with a supervisor card; and an indicator of a central location which is a cache on the supervisor card, an external storage device attached to the supervisor card, an external storage device attached to a line card, and a dedicated line card for storage.

The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. The computer-readable storage medium includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer-readable media now known or later developed.

The methods and processes described in the detailed description section can be embodied as code and/or data, which can be stored in a computer-readable storage medium as described above. When a computer system reads and executes the code and/or data stored on the computer-readable storage medium, the computer system performs the methods and processes embodied as data structures and code and stored within the computer-readable storage medium.

Furthermore, the methods and processes described above can be included in hardware modules. For example, the hardware modules can include, but are not limited to, application-specific integrated circuit (ASIC) chips, field-programmable gate arrays (FPGAs), and other programmable-logic devices now known or later developed. When the hardware modules are activated, the hardware modules perform the methods and processes included within the hardware modules.

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims. 

What is claimed is:
 1. A forwarding device, comprising: a plurality of components, including one or more line cards and a supervisor card, wherein the components perform a method, the method comprising: receiving, by an ingress line card of the forwarding device, a content object with a name; in response to determining a distributed storage technique: storing, by a selected line card, the content object in a location which is a cache of the selected line card; creating, by the selected line card, a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored; transmitting, by the selected line card, a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry; and creating, by a respective other component, a second entry in a table for the respective other component, wherein the second entry matches the first entry.
 2. The forwarding device of claim 1, wherein the selected line card is one or more of the ingress line card and an egress line card, wherein if the selected line card is the egress line card, the method further comprises transmitting, by the ingress line card, the content object to the egress line card, and wherein if the selected line card is both the ingress line card and the egress line card: storing the content object, creating the first entry, and transmitting the first notification message are performed by the ingress line card, and storing the content object, creating the first entry, and transmitting the first notification message are performed by the egress line card.
 3. The forwarding device of claim 1, wherein transmitting the first notification message further comprises: marking, by the selected line card, the first entry as active; and multicasting, by the selected line card, the first notification message to the other components.
 4. The forwarding device of claim 1, wherein transmitting the first notification message further comprises: marking, by the selected line card, the first entry as inactive; transmitting, by the selected line card to the supervisor card, a request to cache the content object at the location; and in response to accepting, by the supervisor card, the request to cache the content object at the location: multicasting, by the supervisor card, the first notification message to the other components; marking, by the selected line card, the first entry as active; and creating, by the respective other component, the second entry in the table for the respective other component.
 5. The forwarding device of claim 4, wherein the method further comprises: in response to not accepting, by the supervisor card, the request to cache the content object at the location, removing, by the selected line card, the first entry from the table of the selected line card based on a timeout of the first entry.
 6. The forwarding device of claim 1, wherein in response to determining a centralized storage technique, the method further comprises: transmitting, by the ingress line card, the content object to the supervisor card; storing, by the supervisor card, the content object in a central location which is associated with the supervisor card; creating, by the supervisor card, a third entry in a table of the supervisor card, wherein the third entry indicates the content object name and further indicates the supervisor card as the central location in which the content object is stored; transmitting, by the supervisor card, a second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry; and creating, by a respective other component, a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry.
 7. The forwarding device of claim 6, wherein the central location is one or more of: a cache on the supervisor card; an external storage device attached to the supervisor card; an external storage device attached to a line card; and a dedicated line card for storage, wherein the dedicated line card is accessed only by the supervisor card.
 8. The forwarding device of claim 7, wherein if the central location is the external storage device attached to the supervisor card, the external storage device attached to the line card, or the dedicated line card for storage, the method further comprises: transmitting, by the supervisor card, the content object to the central location.
 9. The forwarding device of claim 7, wherein transmitting the second notification message further comprises: creating, by the external storage device attached to the line card or the dedicated line card for storage, the third entry in a table of the external storage device attached to the line card or the dedicated line card for storage; and transmitting, by the external storage device attached to the line card or the dedicated line card for storage, the second notification message to the other components.
 10. The forwarding device of claim 6, wherein transmitting the second notification message further comprises multicasting, by the supervisor card, the second notification message to the other components.
 11. A computer-implemented method, comprising: receiving, by an ingress line card of a forwarding device, a content object with a name, wherein the forwarding device comprises a plurality of components, including one or more line cards and a supervisor card; in response to determining a distributed storage technique: storing, by a selected line card, the content object in a location which is a cache of the selected line card; creating, by the selected line card, a first entry in a table of the selected line card, wherein the first entry indicates the content object name and the location in which the content object is stored; transmitting, by the selected line card, a first notification message to other components, wherein the first notification message indicates the content object name and the location indicated in the first entry; and creating, by a respective other component, a second entry in a table for the respective other component, wherein the second entry matches the first entry.
 12. The method of claim 11, wherein the selected line card is one or more of the ingress line card and an egress line card, wherein if the selected line card is an egress line card, the method further comprises transmitting, by the ingress line card, the content object to the egress line card, and wherein if the selected line card is both the ingress line card and the egress line card: storing the content object, creating the first entry, and transmitting the first notification message are performed by the ingress line card, and storing the content object, creating the first entry, and transmitting the first notification message are performed by the egress line card.
 13. The method of claim 11, wherein transmitting the first notification message further comprises: marking, by the selected line card, the first entry as active; and multicasting, by the selected line card, the first notification message to the other components.
 14. The method of claim 11, wherein transmitting the first notification message further comprises: marking, by the selected line card, the first entry as inactive; transmitting, by the selected line card to the supervisor card, a request to cache the content object at the location; and in response to accepting, by the supervisor card, the request to cache the content object at the location: multicasting, by the supervisor card, the first notification message to the other components; marking, by the selected line card, the first entry as active; and creating, by the respective other component, the second entry in the table for the respective other component.
 15. The method of claim 14, further comprising: in response to not accepting, by the supervisor card, the request to cache the content object at the location, removing, by the selected line card, the first entry from the table of the selected line card based on a timeout of the first entry.
 16. The method of claim 11, wherein in response to determining a centralized storage technique, the method further comprises: transmitting, by the ingress line card, the content object to the supervisor card; storing, by the supervisor card, the content object in a central location which is associated with the supervisor card; creating, by the supervisor card, a third entry in a table of the supervisor card, wherein the third entry indicates the content object name and further indicates the supervisor card as the central location in which the content object is stored; transmitting, by the supervisor card, a second notification message to the other components, wherein the second notification message indicates the content object name and the location indicated in the third entry; and creating, by a respective other component, a fourth entry in a table for the respective other component, wherein the fourth entry matches the third entry.
 17. The method of claim 16, wherein the central location is one or more of: a cache on the supervisor card; an external storage device attached to the supervisor card; an external storage device attached to a line card; and a dedicated line card for storage, wherein the dedicated line card is accessed only by the supervisor card.
 18. The method of claim 17, wherein if the central location is the external storage device attached to the supervisor card, the external storage device attached to the line card, or the dedicated line card for storage, the method further comprises: transmitting, by the supervisor card, the content object to the central location.
 19. The method of claim 17, wherein transmitting the second notification message further comprises: creating, by the external storage device attached to the line card or the dedicated line card for storage, the third entry in a table of the external storage device attached to the line card or the dedicated line card for storage; and transmitting, by the external storage device attached to the line card or the dedicated line card for storage, the second notification message to the other components.
 20. The method of claim 16, wherein transmitting the second notification message further comprises multicasting, by the supervisor card, the second notification message to the other components. 